import java.sql.*; import java.util.*; public class DbWrapper { // 定义连接池对象为静态变量,将一直存在,直到工作目录关闭。 private static DataSource ds = null;</td> </tr> </table>
// 1.用连接池的方式获得连接 // 如果不是做多数据库程序,推荐使用此方法 // 相关内容:在tomcat管理界面配置连接池 public static Connection openConnection() throws Exception { // 只需要初始化1次 if ( ds == null ) { Context initContext = new InitialContext(); Context envContext = (Context) initContext.lookup("java:/comp/env"); DataSource ds = (DataSource) envContext.lookup("jdbc/MyDataSource"); } return ds.getConnection(); } // 2.用jdbc驱动获得连接 // 相关内容:JSP数据库连接大全 public static Connection openConnection( String driver, String url, String username, String password) throws Exception { Class.forName(driver).newInstance(); return DriverManager.getConnection(url, username, password); } public static void closeConnection(Connection conn) throws Exception { if ( conn != null ) { conn.close(); } }
public static int executeUpdate(String sql) throws Exception { int count = 0; Connection conn = null; Statement stmt = null; try { conn = openConnection(); stmt = conn.createStatement(); count = stmt.executeUpdate(sql); } catch ( Exception e ) { throw e; } finally { closeConnection(conn); } return count; } public static List executeQuery(String sql) throws Exception { List list = new ArrayList(); Connection conn = null; Statement stmt = null; ResultSet rs = null; try { conn = openConnection(); stmt = conn.createStatement(); rs = stmt.executeQuery(sql); ResultSetMetaData rsmd = rs.getMetaData(); while ( rs.next() ) { Map map = new HashMap(); for ( int i = 1; i <= rsmd.getColumnCount(); i++ ) { map.put(rsmd.getColumnName(i), rs.getObject(i)); } list.add(map); }
} catch ( Exception e ) { e.printStackTrace(); } finally { if ( rs != null ) rs.close(); closeConnection(conn); } return list;
} }
// 1.对于insert, update, delete语句</td> </tr> </table>
int count = DbWrapper.executeUpdate(sql);
// 2.对于selete语句 java.util.List list = DbWrapper.executeQuery(sql);
// 方法一:按名字取值,注意大小写是严格区分的 for ( int i = 0; i < list.size(); i++ ) { java.util.Map map = (java.util.Map)list.get(i); out.println(mag.get("column_name").toString()); }
// 方法二:遍历取值 for ( int i = 0; i < list.size(); i++ ) { java.util.Map map = (java.util.Map)list.get(i);
for (java.util.Iterator it = map.keySet().iterator(); it.hasNext();) { String column_name = it.next().toString());
// 取值时注意null判断 out.println(column_name + " = " + map.get(column_name) == null ? "" :
map.get(column_name).toString()); } }
</td> </tr> </table> </td> </tr> <tr>
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